Engine Help?

Yesterday I left my hood open while it rained & This morning It was acting strange. The engine light was not on & was running normal temperature but it was "Bogging Down" Kinda like 1 piston wasn't working.
Any ideas of what is wrong is much appreciated. Thanks & God Bless

Yesterday I left my hood open while it rained & This morning It was acting strange. The engine light was not on & was running normal temperature but it was "Bogging Down" Kinda like 1 piston wasn't working.
Any ideas of what is wrong is much appreciated. Thanks & God Bless

Welcome to the forum, 5.8longbed; I'm the Ford Service rep here. What's your truck's model year and mileage? Have you had your dealership inspect?